Effect of Concentration on HPAM Retention in Porous Media

Guoyin Zhang, R.S. Seright – 2014

Abstract

This paper investigates the effect of HPAM polymer concentration on retention in porous media using both static and dynamic measurements. Results show that different retention behaviors exist in dilute, semidilute, and concentrated regions. In dilute and concentrated regions, retention has little dependence on concentration. In the semidilute region, retention is concentration dependent. If a porous medium is first contacted with dilute polymer solution sufficient to satisfy retention, no significant additional retention occurs upon exposure to higher concentrations. A concentration-related retention mechanism is proposed considering adsorbed polymer molecule orientation and molecular coil interactions. In the semidilute region, moderate coil interactions lead to mixed adsorbed-polymer orientation and concentration-dependent retention. Practical implication: reduced polymer retention may be achieved in field applications by first injecting a low-concentration polymer bank.

Key Takeaways

  • HPAM polymer retention shows three distinct concentration regimes: in the dilute and concentrated regions, retention is largely independent of concentration; in the semidilute region, retention depends on concentration.
  • Pre-saturating a porous medium with dilute polymer solution sufficient to satisfy its retention capacity prevents significant additional retention when the concentration is subsequently increased — a directly actionable field design insight.
  • A proposed mechanism explains concentration-dependent retention through adsorbed polymer molecule orientation and coil-coil interactions: in the semidilute region, entangled coils lead to mixed adsorption geometry and higher retention.
  • Static and dynamic retention measurements give consistent results when properly designed — validating the use of simpler static screening tests to predict dynamic retention behavior in core material.
  • In field polymer flood applications, injecting a pre-flush of low-concentration polymer bank before the main high-concentration slug may reduce total polymer retention and improve economic efficiency.
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